/* An expandable hash tables datatype.
- Copyright (C) 1999 Free Software Foundation, Inc.
+ Copyright (C) 1999, 2000, 2001 Free Software Foundation, Inc.
Contributed by Vladimir Makarov (vmakarov@cygnus.com).
This file is part of the libiberty library.
#include <stdlib.h>
#endif
+#ifdef HAVE_STRING_H
+#include <string.h>
+#endif
+
#include <stdio.h>
#include "libiberty.h"
/* This macro defines reserved value for empty table entry. */
-#define EMPTY_ENTRY ((void *) 0)
+#define EMPTY_ENTRY ((PTR) 0)
/* This macro defines reserved value for table entry which contained
a deleted element. */
-#define DELETED_ENTRY ((void *) 1)
+#define DELETED_ENTRY ((PTR) 1)
+
+static unsigned long higher_prime_number PARAMS ((unsigned long));
+static hashval_t hash_pointer PARAMS ((const void *));
+static int eq_pointer PARAMS ((const void *, const void *));
+static int htab_expand PARAMS ((htab_t));
+static PTR *find_empty_slot_for_expand PARAMS ((htab_t, hashval_t));
+
+/* At some point, we could make these be NULL, and modify the
+ hash-table routines to handle NULL specially; that would avoid
+ function-call overhead for the common case of hashing pointers. */
+htab_hash htab_hash_pointer = hash_pointer;
+htab_eq htab_eq_pointer = eq_pointer;
-/* The following function returns the nearest prime number which is
- greater than given source number. */
+/* The following function returns a nearest prime number which is
+ greater than N, and near a power of two. */
static unsigned long
higher_prime_number (n)
unsigned long n;
{
- unsigned long i;
-
- n |= 0x01; /* Force N to be odd. */
- if (n < 9)
- return n; /* All odd numbers < 9 are prime. */
+ /* These are primes that are near, but slightly smaller than, a
+ power of two. */
+ static const unsigned long primes[] = {
+ (unsigned long) 2,
+ (unsigned long) 7,
+ (unsigned long) 13,
+ (unsigned long) 31,
+ (unsigned long) 61,
+ (unsigned long) 127,
+ (unsigned long) 251,
+ (unsigned long) 509,
+ (unsigned long) 1021,
+ (unsigned long) 2039,
+ (unsigned long) 4093,
+ (unsigned long) 8191,
+ (unsigned long) 16381,
+ (unsigned long) 32749,
+ (unsigned long) 65521,
+ (unsigned long) 131071,
+ (unsigned long) 262139,
+ (unsigned long) 524287,
+ (unsigned long) 1048573,
+ (unsigned long) 2097143,
+ (unsigned long) 4194301,
+ (unsigned long) 8388593,
+ (unsigned long) 16777213,
+ (unsigned long) 33554393,
+ (unsigned long) 67108859,
+ (unsigned long) 134217689,
+ (unsigned long) 268435399,
+ (unsigned long) 536870909,
+ (unsigned long) 1073741789,
+ (unsigned long) 2147483647,
+ /* 4294967291L */
+ ((unsigned long) 2147483647) + ((unsigned long) 2147483644),
+ };
+
+ const unsigned long *low = &primes[0];
+ const unsigned long *high = &primes[sizeof(primes) / sizeof(primes[0])];
+
+ while (low != high)
+ {
+ const unsigned long *mid = low + (high - low) / 2;
+ if (n > *mid)
+ low = mid + 1;
+ else
+ high = mid;
+ }
- next:
- n += 2;
- i = 3;
- do
+ /* If we've run out of primes, abort. */
+ if (n > *low)
{
- if (n % i == 0)
- goto next;
- i += 2;
+ fprintf (stderr, "Cannot find prime bigger than %lu\n", n);
+ abort ();
}
- while ((i * i) <= n);
- return n;
+ return *low;
+}
+
+/* Returns a hash code for P. */
+
+static hashval_t
+hash_pointer (p)
+ const PTR p;
+{
+ return (hashval_t) ((long)p >> 3);
+}
+
+/* Returns non-zero if P1 and P2 are equal. */
+
+static int
+eq_pointer (p1, p2)
+ const PTR p1;
+ const PTR p2;
+{
+ return p1 == p2;
}
/* This function creates table with length slightly longer than given
source length. Created hash table is initiated as empty (all the
hash table entries are EMPTY_ENTRY). The function returns the
- created hash table. */
+ created hash table. Memory allocation must not fail. */
htab_t
-htab_create (size, hash_f, eq_f)
+htab_create (size, hash_f, eq_f, del_f)
size_t size;
htab_hash hash_f;
htab_eq eq_f;
+ htab_del del_f;
{
htab_t result;
size = higher_prime_number (size);
result = (htab_t) xcalloc (1, sizeof (struct htab));
- result->entries = (void **) xcalloc (size, sizeof (void *));
+ result->entries = (PTR *) xcalloc (size, sizeof (PTR));
result->size = size;
result->hash_f = hash_f;
result->eq_f = eq_f;
+ result->del_f = del_f;
+ result->return_allocation_failure = 0;
+ return result;
+}
+
+/* This function creates table with length slightly longer than given
+ source length. The created hash table is initiated as empty (all the
+ hash table entries are EMPTY_ENTRY). The function returns the created
+ hash table. Memory allocation may fail; it may return NULL. */
+
+htab_t
+htab_try_create (size, hash_f, eq_f, del_f)
+ size_t size;
+ htab_hash hash_f;
+ htab_eq eq_f;
+ htab_del del_f;
+{
+ htab_t result;
+
+ size = higher_prime_number (size);
+ result = (htab_t) calloc (1, sizeof (struct htab));
+ if (result == NULL)
+ return NULL;
+
+ result->entries = (PTR *) calloc (size, sizeof (PTR));
+ if (result->entries == NULL)
+ {
+ free (result);
+ return NULL;
+ }
+
+ result->size = size;
+ result->hash_f = hash_f;
+ result->eq_f = eq_f;
+ result->del_f = del_f;
+ result->return_allocation_failure = 1;
return result;
}
htab_delete (htab)
htab_t htab;
{
+ int i;
+
+ if (htab->del_f)
+ for (i = htab->size - 1; i >= 0; i--)
+ if (htab->entries[i] != EMPTY_ENTRY
+ && htab->entries[i] != DELETED_ENTRY)
+ (*htab->del_f) (htab->entries[i]);
+
free (htab->entries);
free (htab);
}
htab_empty (htab)
htab_t htab;
{
- memset (htab->entries, 0, htab->size * sizeof (void *));
+ int i;
+
+ if (htab->del_f)
+ for (i = htab->size - 1; i >= 0; i--)
+ if (htab->entries[i] != EMPTY_ENTRY
+ && htab->entries[i] != DELETED_ENTRY)
+ (*htab->del_f) (htab->entries[i]);
+
+ memset (htab->entries, 0, htab->size * sizeof (PTR));
+}
+
+/* Similar to htab_find_slot, but without several unwanted side effects:
+ - Does not call htab->eq_f when it finds an existing entry.
+ - Does not change the count of elements/searches/collisions in the
+ hash table.
+ This function also assumes there are no deleted entries in the table.
+ HASH is the hash value for the element to be inserted. */
+
+static PTR *
+find_empty_slot_for_expand (htab, hash)
+ htab_t htab;
+ hashval_t hash;
+{
+ size_t size = htab->size;
+ hashval_t hash2 = 1 + hash % (size - 2);
+ unsigned int index = hash % size;
+
+ for (;;)
+ {
+ PTR *slot = htab->entries + index;
+
+ if (*slot == EMPTY_ENTRY)
+ return slot;
+ else if (*slot == DELETED_ENTRY)
+ abort ();
+
+ index += hash2;
+ if (index >= size)
+ index -= size;
+ }
}
/* The following function changes size of memory allocated for the
entries and repeatedly inserts the table elements. The occupancy
of the table after the call will be about 50%. Naturally the hash
table must already exist. Remember also that the place of the
- table entries is changed. */
+ table entries is changed. If memory allocation failures are allowed,
+ this function will return zero, indicating that the table could not be
+ expanded. If all goes well, it will return a non-zero value. */
-static void
+static int
htab_expand (htab)
htab_t htab;
{
- void **oentries;
- void **olimit;
- void **p;
+ PTR *oentries;
+ PTR *olimit;
+ PTR *p;
oentries = htab->entries;
olimit = oentries + htab->size;
htab->size = higher_prime_number (htab->size * 2);
- htab->entries = xcalloc (htab->size, sizeof (void **));
+
+ if (htab->return_allocation_failure)
+ {
+ PTR *nentries = (PTR *) calloc (htab->size, sizeof (PTR *));
+ if (nentries == NULL)
+ return 0;
+ htab->entries = nentries;
+ }
+ else
+ htab->entries = (PTR *) xcalloc (htab->size, sizeof (PTR *));
htab->n_elements -= htab->n_deleted;
htab->n_deleted = 0;
p = oentries;
do
{
- void *x = *p;
+ PTR x = *p;
+
if (x != EMPTY_ENTRY && x != DELETED_ENTRY)
{
- void **q = htab_find_slot (htab, x, 1);
+ PTR *q = find_empty_slot_for_expand (htab, (*htab->hash_f) (x));
+
*q = x;
}
+
p++;
}
while (p < olimit);
+
free (oentries);
+ return 1;
}
/* This function searches for a hash table entry equal to the given
element. It cannot be used to insert or delete an element. */
-void *
-htab_find (htab, element)
+PTR
+htab_find_with_hash (htab, element, hash)
htab_t htab;
- const void *element;
+ const PTR element;
+ hashval_t hash;
{
- unsigned int index, hash, hash2;
+ unsigned int index;
+ hashval_t hash2;
size_t size;
+ PTR entry;
htab->searches++;
size = htab->size;
- hash = (*htab->hash_f) (element);
- hash2 = 1 + hash % (size - 2);
index = hash % size;
+ entry = htab->entries[index];
+ if (entry == EMPTY_ENTRY
+ || (entry != DELETED_ENTRY && (*htab->eq_f) (entry, element)))
+ return entry;
+
+ hash2 = 1 + hash % (size - 2);
+
for (;;)
{
- void *entry = htab->entries[index];
- if (entry == EMPTY_ENTRY)
- return NULL;
- else if (entry != DELETED_ENTRY && (*htab->eq_f) (entry, element))
- return entry;
-
htab->collisions++;
index += hash2;
if (index >= size)
index -= size;
+
+ entry = htab->entries[index];
+ if (entry == EMPTY_ENTRY
+ || (entry != DELETED_ENTRY && (*htab->eq_f) (entry, element)))
+ return entry;
}
}
+/* Like htab_find_slot_with_hash, but compute the hash value from the
+ element. */
+
+PTR
+htab_find (htab, element)
+ htab_t htab;
+ const PTR element;
+{
+ return htab_find_with_hash (htab, element, (*htab->hash_f) (element));
+}
+
/* This function searches for a hash table slot containing an entry
equal to the given element. To delete an entry, call this with
INSERT = 0, then call htab_clear_slot on the slot returned (possibly
after doing some checks). To insert an entry, call this with
- INSERT = 1, then write the value you want into the returned slot. */
+ INSERT = 1, then write the value you want into the returned slot.
+ When inserting an entry, NULL may be returned if memory allocation
+ fails. */
-void **
-htab_find_slot (htab, element, insert)
+PTR *
+htab_find_slot_with_hash (htab, element, hash, insert)
htab_t htab;
- const void *element;
- int insert;
+ const PTR element;
+ hashval_t hash;
+ enum insert_option insert;
{
- void **first_deleted_slot;
- unsigned int index, hash, hash2;
+ PTR *first_deleted_slot;
+ unsigned int index;
+ hashval_t hash2;
size_t size;
- if (insert && htab->size * 3 <= htab->n_elements * 4)
- htab_expand (htab);
+ if (insert == INSERT && htab->size * 3 <= htab->n_elements * 4
+ && htab_expand (htab) == 0)
+ return NULL;
size = htab->size;
- hash = (*htab->hash_f) (element);
hash2 = 1 + hash % (size - 2);
index = hash % size;
for (;;)
{
- void *entry = htab->entries[index];
+ PTR entry = htab->entries[index];
if (entry == EMPTY_ENTRY)
{
- if (!insert)
+ if (insert == NO_INSERT)
return NULL;
htab->n_elements++;
if (!first_deleted_slot)
first_deleted_slot = &htab->entries[index];
}
- else
- {
- if ((*htab->eq_f) (entry, element))
- return &htab->entries[index];
- }
+ else if ((*htab->eq_f) (entry, element))
+ return &htab->entries[index];
htab->collisions++;
index += hash2;
}
}
+/* Like htab_find_slot_with_hash, but compute the hash value from the
+ element. */
+
+PTR *
+htab_find_slot (htab, element, insert)
+ htab_t htab;
+ const PTR element;
+ enum insert_option insert;
+{
+ return htab_find_slot_with_hash (htab, element, (*htab->hash_f) (element),
+ insert);
+}
+
/* This function deletes an element with the given value from hash
table. If there is no matching element in the hash table, this
function does nothing. */
void
htab_remove_elt (htab, element)
htab_t htab;
- void *element;
+ PTR element;
{
- void **slot;
+ PTR *slot;
- slot = htab_find_slot (htab, element, 0);
+ slot = htab_find_slot (htab, element, NO_INSERT);
if (*slot == EMPTY_ENTRY)
return;
+ if (htab->del_f)
+ (*htab->del_f) (*slot);
+
*slot = DELETED_ENTRY;
htab->n_deleted++;
}
void
htab_clear_slot (htab, slot)
htab_t htab;
- void **slot;
+ PTR *slot;
{
if (slot < htab->entries || slot >= htab->entries + htab->size
|| *slot == EMPTY_ENTRY || *slot == DELETED_ENTRY)
abort ();
+
+ if (htab->del_f)
+ (*htab->del_f) (*slot);
+
*slot = DELETED_ENTRY;
htab->n_deleted++;
}
htab_traverse (htab, callback, info)
htab_t htab;
htab_trav callback;
- void *info;
+ PTR info;
{
- void **slot, **limit;
- slot = htab->entries;
- limit = slot + htab->size;
+ PTR *slot = htab->entries;
+ PTR *limit = slot + htab->size;
+
do
{
- void *x = *slot;
+ PTR x = *slot;
+
if (x != EMPTY_ENTRY && x != DELETED_ENTRY)
- if (!(*callback) (x, info))
+ if (!(*callback) (slot, info))
break;
}
while (++slot < limit);
}
-/* The following function returns current size of given hash table. */
+/* Return the current size of given hash table. */
size_t
htab_size (htab)
return htab->size;
}
-/* The following function returns current number of elements in given
- hash table. */
+/* Return the current number of elements in given hash table. */
size_t
htab_elements (htab)
return htab->n_elements - htab->n_deleted;
}
-/* The following function returns number of percents of fixed
- collisions during all work with given hash table. */
+/* Return the fraction of fixed collisions during all work with given
+ hash table. */
double
htab_collisions (htab)
htab_t htab;
{
- int searches;
-
- searches = htab->searches;
- if (searches == 0)
+ if (htab->searches == 0)
return 0.0;
- return (double)htab->collisions / (double)searches;
+
+ return (double) htab->collisions / (double) htab->searches;
+}
+
+/* Hash P as a null-terminated string.
+
+ Copied from gcc/hashtable.c. Zack had the following to say with respect
+ to applicability, though note that unlike hashtable.c, this hash table
+ implementation re-hashes rather than chain buckets.
+
+ http://gcc.gnu.org/ml/gcc-patches/2001-08/msg01021.html
+ From: Zack Weinberg <zackw@panix.com>
+ Date: Fri, 17 Aug 2001 02:15:56 -0400
+
+ I got it by extracting all the identifiers from all the source code
+ I had lying around in mid-1999, and testing many recurrences of
+ the form "H_n = H_{n-1} * K + c_n * L + M" where K, L, M were either
+ prime numbers or the appropriate identity. This was the best one.
+ I don't remember exactly what constituted "best", except I was
+ looking at bucket-length distributions mostly.
+
+ So it should be very good at hashing identifiers, but might not be
+ as good at arbitrary strings.
+
+ I'll add that it thoroughly trounces the hash functions recommended
+ for this use at http://burtleburtle.net/bob/hash/index.html, both
+ on speed and bucket distribution. I haven't tried it against the
+ function they just started using for Perl's hashes. */
+
+hashval_t
+htab_hash_string (p)
+ const PTR p;
+{
+ const unsigned char *str = (const unsigned char *) p;
+ hashval_t r = 0;
+ unsigned char c;
+
+ while ((c = *str++) != 0)
+ r = r * 67 + c - 113;
+
+ return r;
}
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